package com.summer.sqlSession;

import com.summer.pojo.Configuration;
import com.summer.pojo.MappedStatement;

import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;
    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {
        //将要去完成simpleExecutor里面的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size() == 1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public <T> T getMapper(Class<T> mapperClass) {
        //使用jdk动态代理来为Dao接口生成代理对象，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            //代理对象调用接口中的任意方法，都会执行invoke方法
            //参数1：当前代理对象的应用
            //参数2：当前被调用方法的引用
            //参数3：传递的参数
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层都还是去执行jdbc 根据不同情况 来调用selectOne selectList
                //准备参数：statementid = namespace.id = 接口全限定名.方法名
                //方法名
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className + "." + methodName;
                //准备参数2： params args

                //获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                //判定是否进行了 泛型类型参数化  //判定返回值类型

                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }
                if(methodName.startsWith("update")){
                    return update(statementId, args);
                }
                if(methodName.startsWith("delete")){
                    return delete(statementId, args);
                }
                //TODO 如果是基本类型的包装类怎么判断呢
                //SqlCommand command;
                //Class<?> caller = Reflection.getCallerClass();

                return selectOne(statementId,args);
            }
        });
        return (T) proxyInstance;
    }

    @Override
    public Integer update(String statementid, Object... params) throws SQLException, ClassNotFoundException {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer update = simpleExecutor.update(configuration, mappedStatement, params);
        return update;
    }

    @Override
    public Integer delete(String statementid, Object... params) throws SQLException, ClassNotFoundException {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer delete = simpleExecutor.delete(configuration, mappedStatement, params);
        return delete;
    }


}
